In two-drum winders, in which narrower component webs slit with a slitter-winder from a web unwound from a machine reel are wound into customer rolls, the rolls are usually placed side by side on two winding drums. Because of variations in the cross-direction profiles, for example, thickness, moisture and roughness, of the web to be wound, adjacent rolls are not formed with precisely equally large diameters, in spite of the fact that, in principle, precisely equally long component webs are wound into them. Owing to the different diameters of the rolls, the roll cores placed in the roll centres are displaced with the progress of winding in relation to one another so that their centres of rotation are separated and, at the same time, minor variations also occur in the angular speeds of the rolls. Since the roll centres are, however, in contact with each other during the entire winding process, diverting forces arise between the ends of the roll cores, and the rolls tend to “jump”, in which connection the rolls that are being formed can be damaged. Owing to this detrimental vibration, in two-drum winding, it is generally necessary to run at a lower speed, i.e. to be content with a lower winding speed, which reduces the capacity of the machine and is, thus, uneconomical.
The problem described above has occurred as long as winders of the two-drum type have been in use. The seriousness of the problem has, however, varied in the course of the years, because the profile of the web produced on a paper machine has improved and, at the same time, the roll size and the winding speed have changed only to a small extent. In recent years, the diameters of the customer rolls produced have started becoming ever larger and, at the same time, the winding speeds have also increased, for which reason the problem of vibration has been noticed again: even a little variation of profile in the direction of width of the web is cumulated especially during winding of thin paper grades so that faults in the shape of the rolls which arise from the web profile cause a significant vibration problem.
In the winding process, a number of different phenomena are effective which attempt to shift the web rolls that are being formed in their axial direction:                deflection of winding cylinders, i.e. winding drums,        faults in the shape of the rolls arising from uneven profile of the web, and        also the core chucks, which support the roll cores of the outermost web rolls, subject the row of rolls to axial forces when they keep the row of rolls in the desired position.        
The core chucks alone can also produce a compression force applied to the whole row of roll cores when the roll cores are excessively long: the total length of the roll cores is higher than the regulated distance between the core chucks.
One problem in winding is also that the length of the roll cores, for example, roll spools, changes during winding because with some core and paper qualities the compression pressure caused by the web being wound onto the core gives rise to elongation of cores.
When roll cores are pressed in their position at their ends by means of core chucks, another problem is often that there is either too much or too little pressing. In a situation where the core chucks press too much, the vibration problems described above arise and if the chucks are again too loose, there are lateral shifts. Because of the problems of the type described above, determining of the correct pressing force and position of the core chucks is very problematic.
The phenomena described above can, either alone or together, produce situations in which the rolls or the ends of the roll cores tend to be pressed against each other and thereby to produce a relative support force, thus causing vibration problems.
Thus, there are several factors that produce a relative axial thrust force between the rolls. The core chucks, which keep the outermost roll cores in their positions, keep the row of rolls in the correct winding position in the lateral direction, but deflection of the winding drums drives the rolls towards the lowest point of deflection. Variations in the web profile produce a “carrot shape” even in individual rolls, in which case the rolls tend to move in the lateral direction. Of course, variations in the lengths of the roll cores, together with the core chucks, cause variation in the axial forces in different forms. It comes out from the above that there are a number of different reasons why the rolls tend to be pressed against each other during winding, thus generating vibration that limits running speeds and even damages the rolls.
The problems described above occur in all such winder types in which the location/support of the web rolls that are formed comply with the following terms:                the roll cores (web rolls) are placed one after the other coaxially so that the location of each roll core is determined by means of the adjacent roll cores,        the roll cores (web rolls) are supported under optimal conditions in the radial direction of the rolls only (the core chucks just prevent axial movement arising from faults in the roll shapes and from deflection of the winding members).        